Modeling and simulation of hydrogels for the application as bending actuators

Abstract

Polyelectrolyte gels show a quite large swelling or bending behavior under external physical, chemical, thermal or electrical stimulation. In this paper the bending actuation of polyelectrolyte gels under applied electric fields is studied and the mechanisms occurring in polyelectrolyte gels due to the applied stimulus are investigated.In the present research, a complete formulation for describing actuation of polyelectrolyte gels in a solution bath is presented. First, the kinematics, the balance laws of continuum chemo-electro-mechanics and the constitutive equations of the involved fields are given.Then, in the numerical simulation part, the changes of the mobile concentrations, of the electric potential and the displacements in the gel domain are shown. It is demonstrated by a comparison between a chemo-electrical and a chemo-electro-mechanical test case, that the full coupling also leads to a change of the concentration of bound groups resulting in alterations of the local concentrations of the mobile ions, of the electric potential and again of the local gel displacement. It will be shown, that the presented coupled multi-field model is predestined for investigating electrical stimulation of hydrogels, and for simulating hydrogel bending actuation.